Thermoplastic polymers are used in a wide variety of applications. However, thermoplastic polymers, such as polypropylene and polyethylene, pose additional challenges compared to other polymer species, especially with respect to formation of, for example, fibers. This is because the material and processing requirements for production of fibers are much more stringent than for producing other forms, for example, films. For the production of fibers, polymer melt flow characteristics are more demanding on the material's physical and rheological properties vs other polymer processing methods. Also, the local shear/extensional rate and shear rate are much greater in fiber production than other processes and, for spinning very fine fibers, small defects, slight inconsistencies, or phase incompatibilities in the melt are not acceptable for a commercially viable process. Moreover, high molecular weight thermoplastic polymers cannot be easily or effectively spun into fine fibers. Given their availability and potential strength improvement, it would be desirable to provide a way to easily and effectively spin such high molecular weight polymers.
Most thermoplastic polymers, such as polyethylene, polypropylene, and polyethylene terephthalate, are derived from monomers (e.g., ethylene, propylene, and terephthalic acid, respectively) that are obtained from non-renewable, fossil-based resources (e.g., petroleum, natural gas, and coal). Thus, the price and availability of these resources ultimately have a significant impact on the price of these polymers. As the worldwide price of these resources escalates, so does the price of materials made from these polymers. Furthermore, many consumers display an aversion to purchasing products that are derived solely from petrochemicals. In some instances, consumers are hesitant to purchase products made from non-renewable fossil-based resources, which are non-renewable fossil based resources. Other consumers may have adverse perceptions about products derived from petrochemicals as being “unnatural” or not environmentally friendly.
Thermoplastic polymers and thermoplastic starches are often incompatible with, or have poor miscibility with additives (e.g., oils, pigments, organic dyes, perfumes, etc.) that might otherwise contribute to a reduced consumption of these polymers in the manufacture of downstream articles. Heretofore, the art has not effectively addressed how to reduce the amount of thermoplastic polymers derived from non-renewable, fossil-based resources in the manufacture of common articles employing these polymers. Accordingly, it would be desirable to address this deficiency. Existing art has combined polypropylene with additives, with polypropylene as the minor component to form cellular structures. These cellular structures are the purpose behind including renewable materials that are later removed or extracted after the structure is formed. U.S. Pat. No. 3,093,612 describes the combination of polypropylene with various fatty acids where the fatty acid is removed. The scientific paper J. Apply. Polym. Sci 82 (1) pp. 169-177 (2001) discloses use of diluents on polypropylene for thermally induced phase separation to produce an open and large cellular structure but at low polymer ratio, where the diluent is subsequently removed from the final structure. The scientific paper J. Apply. Polym. Sci 105 (4) pp. 2000-2007 (2007) produces microporous membranes via thermally induced phase separation with dibutyl phthalate and soy bean oil mixtures, with a minor component of polypropylene. The diluent is removed in the final structure. The scientific paper Journal of Membrane Science 108 (1-2) pp. 25-36 (1995) produces hollow fiber microporous membranes using soy bean oil and polypropylene mixtures, with a minor component of polypropylene and using thermally induced phase separation to produce the desired membrane structure. The diluent is removed in the final structure. In all of these cases, the diluent as described is removed to produce the final structure. These structures before the diluent is removed are oily with excessive amounts of diluent to produce very open microporous structures with pore sizes>10 μm.
A need exists for molded articles made from compositions of thermoplastic starch and thermoplastic polymers that allow for use of higher molecular weight and/or decreased non-renewable resource based materials, and/or incorporation of further additives, such as perfumes and dyes. A still further need is for molded articles from compositions that leave the additive present to deliver renewable materials in the final product and that can also enable the addition of further additives into the final structure, such as dyes and perfumes, for example.